The antibacterial activity and immunomodulatory effect of naturally synthesized chitosan and silver nanoparticles against Pseudomonas fluorescence infection in Nile tilapia (Oreochromis niloticus): An in vivo study

A sixty-day feeding trial was conducted to assess the effects of silver nanoparticles (AgNPs) and chitosan nanoparticles (CNPs) on the growth and immunity of Nile tilapia (Oreochromis niloticus), compared with the control group. CNPs and AgNPs were green synthesized and added to a control diet (30% crude protein) at levels of 2.0 g CNPs/kg diet and 1.0 mg AgNPs/kg diet. One hundred and eighty fish (101 +/- 3.98 g) were randomly distributed into nine fiberglass tanks (200 cm x 200 cm x 100 cm, twenty fish each) to represent three equal groups (60 fish per group). After one and two months of the feeding trial, parameters of water quality, growth indices, hematology, and liver and kidney biomarkers were evaluated. At the end of the experiment, 10 fish from each group were challenged experimentally via the intraperitoneal injection with Pseudomonas fluorescence and fish mortality was observed for further ten days. Then, specimens from the liver, kidney, spleen, and anterior intestine were examined to assess the histopathological alterations. Incorporating a 2.0 g CNPs/kg diet was a promising growth enhancer; however, a 1.0 mg AgNPs/kg diet had no effects on tilapia performance. Further-more, AgNPs appeared to reduce water pollution, leading to water filtration via decreasing both total dissolved solids (TDS) and electrical conductivity (EC). A significant role of AgNPs in improving tilapia's erythrogram (RBCs number and Hb concentration) was evident. Compared with the control group, both groups of CNPs and AgNPs improved non-specific immune parameters and showed defense effects against P. fluorescence. The fish mortality after P. fluorescence infection in CNPs and AgNPs-fed fish groups revealed significant decreases (P < 0.05) of 10% and 25%; respectively, while the control group exhibited a mortality rate of 40%. The current investigation evoked that using dietary CNPs (2.0 g/kg feed) as an antibacterial agent against P. fluorescence infection in Nile tilapia culture was better than dietary AgNPs (1.0 mg/kg diet) which, induced cells inflam-mation causing tissues necrosis.